1. Field of the Invention
The invention relates to a cylinder lock, especially for motor vehicles, the cylinder core of which that is provided with a key channel and spring-loaded tumblers is coupled, by means of an axial coupling, with an output member when the cylinder core is turned by means of an appropriate key, and is uncoupled therefrom when the cylinder core is turned by means of an inappropriate key or forcibly by a foreign body. In the course of unauthorized turning of the cylinder core, disengagement of the coupling from the output member of the cylinder lock occurs, so that it is possible to turn the cylinder core of the cylinder lock without any effect on a door lock latch with which the output member of the cylinder lock is mechanically coupled.
2. Description of Related Art
Cylinder locks of this kind, especially for motor vehicles, are already known. The aforementioned coupling or uncoupling of the cylinder core with the output member is accomplished, in most cases, by means of an axial coupling which, in the first end position of its axial translational movement, connects the output member of the cylinder lock with the cylinder core and, in the second end position of its axial translational movement, uncouples the output member of the cylinder lock from the cylinder core.
Cylinder lock constructions of this sort are known, for instance, from the published German applications DE 43 16 223 A1 and DE 196 04 350 A1, in each of which an axially movable cage is turnably supported in a cylindrical internal cavity of the housing, while a cylinder core provided with a key channel and equipped with spring-loaded tumblers is supported in a cylindrical hollow space of the cage. In the event that no appropriate key is fully introduced into the key channel, blocking projections of the tumblers project beyond the outer circumference of the cylinder core and engage in blocking grooves of the cage. Under these circumstances, the cylinder core is connected with the cage for joint turning and, when the cylinder core is being turned, the cage is simultaneously turned with the latter in the housing as well. Because the outer end face of the cage is provided with a detent part provided with a lifting profile that engages a corresponding detent part of the end projection of the housing, there is encountered, during the turning of the cage, a change in its position relative to the housing as a result of the axial movement of the cage. During this axial movement, an axially displaceable coupling, which simultaneously constitutes an output member of the cylinder lock, is shifted out of engagement with the cylinder core, as a result of which the kinematic connection between the cylinder core and the output member is discontinued, and it is possible afterwards to turn the cylinder core without acting on the door lock latch.
A disadvantage of these and similar constructions is that the use of the turnable and axially movable cage either prevents and/or makes considerably more expensive the provision of any additional safety elements between the cylinder core and the housing of the cylinder lock, such as, for instance, any protective measures against the extraction of the cylinder core out of, or its impacting into, the housing.
An annular, axially displaceable coupling is known from the German patent document DE 44 10 783 C1; it is provided at its inner end portion with an entraining recess for coupling with coupling projections provided on the axial extension of the cylinder core, and includes at its outer end portion an arresting projection that is to serve for the engagement with an arresting recess formed in the housing of the cylinder lock. This annular axially displaceable coupling is in permanent turnfast connection with the output member of the cylinder lock, while it engages in the arresting recess in the uncoupled condition from the cylinder core by means of its aforementioned arresting projection, as a result of which the output member of the cylinder lock is arrested in its position. Uncoupling of this annular axially displaceable coupling from the cylinder core is achieved by means of a detent part formed on the end face of the cage that is turnably mounted in the housing of the cylinder lock and is provided with a lifting profile that is entrained by the cylinder core for joint turning therewith in the event of forcible or unauthorized turning of the latter. The aforementioned lifting profile shifts the axially displaceable coupling out of its connection with the cylinder core against the force of a helical spring acting in the opposite direction, and moves the coupling in a turnfast engagement connection with the arresting recess provided in the housing of the cylinder lock.
When it is desired, after an effort to force the cylinder lock open, to open the latter again with the appropriate key, the cylinder core must be turned, jointly with the cage, into an initial position of the cylinder core, in which the relative positions of the detent part and the associated detent counterpart provided at the end face of the cage and at the facing end face of the annular coupling make possible an axial return movement of the coupling with the aid of the aforementioned axial helical spring, as a result of which there is obtained not only uncoupling from the housing but also connection of the coupling with the cylinder core for joint turning therewith.
A disadvantage of this axially displaceable coupling is its complicated and, from the manufacturing standpoint, demanding axial guidance in the housing of the cylinder lock, the need for the utilization of the cage equipped with the detent part for its axial displacement, as well as the use of a less reliable spring element for the axial return displacement of the coupling in engagement with the cylinder core.